Struggling with Organization of Roomy Closet w/ Water Heater

Q: I live in a 500 square foot apartment with my fiancé and two cats. We have 3 giant (okay, giant for size of our apartment) closets: one in the entry; one in the bedroom; and this one in the hallway outside the bathroom. The dimensions are 3' wide by 5' deep. It has 2 shelves that were here when I got here. Doesn't seem so difficult... but there's a water heater back there! It's 22" in diameter and sits in the back right hand corner. Bins kind of work on the shelves. Any suggestions on how to organize the bottom of the closet? The shelves I stuck in front of the water heater don't utilize the space very well. Thanks!